1. Field of the Invention
The present invention relates to an image forming apparatus, particularly to an image forming apparatus capable of automatically recognizing top and bottom of document image.
2. Description of the Prior Art
In recent times, there have been proposed image forming apparatuses having a variety of automatic processing functions such as an apparatus recording two sheets or four sheets of document fed from an automatic document feeding device on one sheet of record paper, an apparatus having book binding function collating record paper on which image is formed and binding it by staplers, and the like.
It is important for effectively using an image forming apparatus having such an automatic processing function to arrange in order top and bottom of plural sheets of document fed by an automatic document feeding device. In case where copies are formed without noticing mixing of document of which top and bottom is reversed which is noticed later, even if one sheet thereof is mixed, the formed copies have to be abandoned. Accordingly, enormous time and expense are dissipated in the case of a large number of copies.
Therefore, there has been proposed an image forming apparatus which automatically determines top and bottom or sideway arrangement of document image and rotates the document image in the normal direction when it discovers document of which top and bottom is reversed, or which is arranged sideways. For example, in an image forming apparatus disclosed in U. S. Pat. No. 5,077,811, samples of data image are selected from image data obtained by scanning document, the samples are compared with separately prepared reference letters whereby top and bottom or a rotational angle of document image is determined and the document image is rotated in the normal direction if modification thereof is necessary.
Also, there has been disclosed a mark recognition apparatus which although not automatically determining top and bottom or sideway arrangement of document image, designates desired region (closed loop) and command in document image by a marker pen and conducts image processing in compliance with the command designating the region, for example, image processing eliminating the designated region, moving image of the designated region to another designated location, etc. (refer to Japanese Laid-Open Patent Application No. 04-170864).
In addition thereto, there has been proposed a technology in which, when a previously designated specific pattern is identified in document image, the specific pattern is converted into white image or eliminated (refer to Japanese Laid-Open Patent Application No. 04-343570 and Japanese Laid-Open Patent Application No. 04-245860).
However, according to the means for selecting samples of letter image from image data obtained by scanning document and determining top and bottom or a rotational angle by comparing the samples with separately prepared reference letters, even in the case of processing by extracting the samples of letter image, a high level image processing of reading letters and comparing them with reference letters is necessary. Therefore, the cost of the apparatus is significantly increased by adding the means for automatically determining top and bottom or sideway arrangement of document image to the image forming apparatus.